| 摘要 |
PROBLEM TO BE SOLVED: To realize the high ratio of a signal to distortion in a feeder-type telephone line interface or a data access apparatus(DAA) by inserting, an additional detection resistor detecting current which flows in a line modulator but does not flow in a shunt adjusting unit. SOLUTION: A modulator 14 contains a second detection resistor used for reducing errors in a telephone line interface 40 by giving the responsibility of all currents which do not flow in a shunt adjusting unit 16. The shunt adjusting unit 16 supplies power extracted from a telephone line not only to other MODEM and/or a data processing circuit, which are required for supplying the DC terminal and the AC modulation of the telephone line, but also to the modulator 14. A detection resistor 18 is used in a control amplifier 24 in the modulator 14 in a feedback loop. An amplifier 24 can correct distortion in the DAA by monitoring current flowing in the detection resistor 18 by the feedback loop.
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